A nursing assistant who worked at Cedars-Sinai Medical Center is under investigation for allegedly sexually assaulting two patients while they were heavily medicated and too weak to resist, according to court records and interviews.

The women came forward separately last year and gave Los Angeles police similar accounts about how a male employee assaulted them while they were being treated at the hospital.

Detectives served a search warrant at Cedars-Sinai earlier this year to obtain disciplinary records for Guillermo Fernando Diaz, a nursing assistant who had been assigned to a heart patient area. Diaz, 56, was fired in July, according to the hospital. He declined to speak to The Times.

A district attorney's spokeswoman said prosecutors are reviewing whether to file criminal charges.

In November, the state's Department of Public Health revoked Diaz's nursing assistant certification after conducting an investigation into the sexual assault allegations. In a letter informing Diaz of its decision, the agency said it had substantiated multiple allegations of unprofessional conduct.

One woman who said she was sexually assaulted said she remains traumatized.

"It's devastating," she said, to be victimized "when you're incapacitated and not yourself and weak and scared." The Times generally does not name alleged victims in sex crime cases.

During the LAPD probe, a detective discovered two older sexual assault accusations by patients against Diaz — one dating back 14 years — as well as a decade-old complaint by a co-worker who claimed Diaz raped her after an office party. None of those cases resulted in criminal charges.

Diaz has been interviewed by police several times in the last 14 years and denied sexually assaulting patients or the co-worker, according to the search warrant.

In the wake of the complaints, Cedars-Sinai has taken steps to link previously separate databases of employee records, patient complaints and other information, said hospital spokeswoman Sally Stewart. She said the hospital made the changes to improve tracking of allegations against individual staff members but added that it would be speculation to say whether the new system would have led to earlier action in Diaz's case.

Stewart noted that Diaz was never charged as a result of separate LAPD probes of sexual assault reports made before last year. The hospital, she said, investigated all of the complaints and encouraged the patients who came forward last year to report what occurred to police.

"The totality of all the allegations is completely unacceptable to Cedars-Sinai," Stewart said.

The LAPD investigation was launched last summer after reports by the two patients.

The first said she had been sedated before surgery in April 2013 when a nursing assistant entered her room and offered her a back rub, according to the warrant. The patient said the employee began rubbing her breast and groin area, the warrant stated.

The patient told police she repeatedly told him to stop and tried to yell at him but was too weak from her medication, according to the court document.

"Relax," she said the employee told her, "this will make you feel good."

She identified Diaz in a police photo lineup as the person who touched her, according to the warrant.

Soon afterward, another former patient told the hospital and police that she had been repeatedly sexually assaulted by a male employee in 2009. She said she did not have enough strength at the time to tell the man to stop.

She said a hospital social worker told her that the description of the employee matched Diaz, the warrant stated. The patient did not identify Diaz as her attacker in a photo lineup, according to the warrant.

As the detective searched the LAPD's database of reports and consulted with the district attorney's office, he found other similar allegations previously reported to police. In each case, prosecutors had declined to file charges.

In 2000, a heart surgery patient reported that a male employee repeatedly sexually assaulted her in Cedars-Sinai, according to the search warrant. A hospital supervisor told police that Diaz matched the description of the employee, the document states.

In an interview with police, Diaz denied the claim, saying the patient might have felt pressure on her genital area as he adjusted her catheter. The patient said she did not want to go to court and her brother told police she had a history of mental problems, according to the warrant.

Four years later, a Cedars-Sinai worker reported that Diaz raped her after a holiday party organized by the hospital, according to the warrant. Diaz told police that the two had consensual sex, the warrant said.

In 2008, a patient who reported being uncomfortable with how a male nursing assistant touched her asked that the employee not be assigned to her, the warrant said, citing an internal hospital report. The description of the employee was similar to Diaz, the warrant said.

In 2010, another patient recovering from surgery reported that a male nurse's assistant sexually assaulted her while adjusting her compression stockings, according to the warrant. Police identified the employee as Diaz, who denied wrongdoing. One of his co-workers who had been helping the patient at the time of the alleged assault told police she did not see Diaz inappropriately touch the patient.

Some patients questioned why Diaz was allowed to remain a Cedars-Sinai employee despite the earlier reports.

One woman told The Times that hospital staff did not take her complaint seriously and dismissed her allegations as dreams she had while on medication. She said she continues to have difficulty sleeping and sees a therapist as a result of the incident.

"I'm very, very angry," she said. "Cedars was supposed to protect me as a patient... They should have protected other patients."

Asked why Cedars-Sinai did not fire Diaz sooner, Stewart said each complaint was fully investigated and that the hospital takes action "based on the findings of our investigations, and the LAPD investigations when they are involved."

She declined to provide the outcome of the hospital's investigations into the complaints, citing the ongoing police probe.

"We are deeply sorry if any of these patients feel they did not receive the quality care and support that Cedars-Sinai is known for," Stewart said.